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fuel system pressure ???

frankytheroach

NAXJA Forum User
Location
montreal
I have a 95 XJ country, almost stock. I'm in the process of doing a head gasket job. At 240000 km (around 144000 miles). It was over heating and i was losing coolant. I have a test port on the fuel rail, and when I depressed the valve to release the pressure, it had almost none. I was under the impression that the fuel rail was kept pressurized at 35psi (aprox.)

The jeep run great, but the gas/mileage just sucks. I get around 22 l./100km (10.6 MPG)in the city and 16l/100km (14.2 MPG) on highway. I drive it very carefuly and gently. It always started great and run very smooth at all speed and RPM. When I put the key to the on position I can hear the fuel pump purr for a second and a half, the the motor start within a half a turn everytime.

Could I have a small leak somewhere and not smell it??? Could the fuel pump overcome such a small leak and rebuild pressure in the fuel system within 1 1/2 second, giving me great start everytime. How can I test my fuel line for leaks.

Gas aint cheap these days in Canada. I love my XJ but my fuel consumption went up 22% in the last few month. It usualy went up in the cold canadian winter, but came back down when spring arrived, but not this year. If anyone has a clue, I'll welcome any advice.

Thanks!

Francis
 
I think only a little fuel will leak out of the test port with the engine off. You should get a fuel pressure gauge and test it with the engine on. I believe it should be 31PSI at idle, and then around 39PSI when you disconnect the vacuum line to the fuel pressure regulator on the end of the fuel injector rail...

Good luck!
 
There are actually two kinds of leakage for the pressure side, one is just pressure, it bleeds down, the second is drainback, it drains the gas out of the lines back into the tank. The first one happens first and then it may get progressively worse to where you have to turn the keyon for 15-30 seconds to pump fuel up. Two fixes too, one is to replace the pump, the second is to use the BMW anti-drainback valve that several here have done.
I don't think your fuel pump has anything to do with milage unless it's pumping it out on the ground..
 
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